Ok, well I would have to disagree with that as well, It may be fun for us warriors but I think many average players don't think fighting an overwhelming enemy (3+ nations, 6x NS) with practically unlimited resources for an extended time period is fun, especially as it literally destroys months, years of hard work and progress. Especially if they are billocked.
If anything, it leads to disgust, and then apathy, and then leaving the game for another one much of the time. I remember being crushed and raided in other online games that I didn't totally dedicate myself to and that's exactly what I did; leave.
Also, turtling is not a treat for the defenders, either, however much the attackers may grumble.